Field of the Invention
The invention relates to polyether esters for the adhesive bonding of textiles, based on terephthalic acid, isophthalic acid, 1,4-butanediol and a polyalkylene ether diol.
For the adhesive bonding of textile substrates, for example of interlining with outer materials, with the aim of achieving a stiffening effect, polymers are used which in most cases are applied--in finely divided form as powders or from a melt--in a regular arrangement to the inner face of one of the textiles to be bonded, then are partially melted by the action of heat and are thereby caused to undergo partial sintering, after which the outer material to be stiffened is ironed on by renewed application of heat under pressure in hot presses.
A number of different copolyesters have already been disclosed as polymers for use as textile hot-pressing powders. These polyesters are of inadequate stability to the effect of organic solvents as are used in the dry cleaning of textiles, insofar as the polyesters contain exclusively radicals of low molecular weight dicarboxylic acids and dialcobols.
Polyesters having such compositions, and their use as textile adhesives, have been described in various references (U.S. Pat. No. 3,669,921, DE-A 19 20 432, U.S. Pat. No. 3,948,859, DE-A 30 37 100 and DE-A 24 35 863). These polyesters are used predominantly for textiles which are usually cleaned only by washing, examples of their use being the stiffening of collars, cuffs and blouses. In order to obtain textile bonds which are resistant both to washing and to dry cleaning, the use of block copolyether esters has been described. For instance (JP-A 54-153 835), as textile adhesive, a polyether ester is recommended which contains a) from 70 to 40 mol % of terephthalic acid radicals, b) from 30 to 60 mol % of isophthalic acid radicals, c) 1,4-butanediol radicals, and d) from 1 to 10% by weight (based on the sum of a) to d)) of radicals of a polyalkylene ether diol having a molar mass of from 0.3 to 6 kg/mol, all incorporated by cocondensation; component d) includes polyethylene glycol, although polytetramethylene glycol is preferred. As a result of the low concentration of component d), such polyesters have a comparatively high melt viscosity, so that relatively high hot-pressing temperatures and/or long ironing-in times or high pressing forces are necessary to produce the adhesive bonds. Thus materials which are relatively temperature-sensitive can under certain circumstances be damaged in this process.
It has also already been disclosed to retain constituents a) to c) and to raise the concentration of constituent d) to from 10 to 33% by weight (calculated as above), constituent d) denoting a radical of polytetramethylene glycol with a molar mass of from 0.6 to 1.3 kg/mol (DE-A 27 05 270). The exclusive use of polytetramethylene glycol when using heightened concentrations of constituent d) is based on the fact that, in increased concentrations, polyethylene glycol increases the sensitivity of such block polyesters to water and impairs the resistance to washing of textile bonds prepared from such polyesters. For instance (DE-A 24 51 369), for mixtures of block polyether esters with dianhydrides and their use for the adhesive bonding of smooth-surface substrates, it has been described that long-chain polyalkylene ether diols incorporated by condensation as soft segments, with a molar ratio of carbon to oxygen of more than about 2.5:1, led in general to block polyesters which showed little swelling in water and were resistant to hydrolysis. Where, therefore, the factor of sensitivity to water is important in terms of the intended use, as in the case of the textile-adhesive polyesters, then it was expedient not to use polyethylene glycol, or at most (JP-A 54-153 835) to use it in low concentrations.
DE-C 31 32 059 describes a polyether ester for the adhesive bonding of textiles, based on terephthalic acid, isophthalic acid, 1,4-butanediol and a polyalkylene ether diol. The molar ratio of terephthalic acid to isophthalic acid in this ester is from 48 to 55:from 52 to 45.
Owing to the high proportion of terephthalic acid, the polyester is highly crystalline, which always leads to problems with adhesion, and has a high melting point, which contradicts the recent trend in bonding. It has been found that, by lowering the proportion of terephthalic acid to from 42 to 45 mol % while raising that of isophthalic acid to from 55 to 58%, it was possible to reduce the crystallinity and the melting point.
The object of the invention was therefore to find a polyether ester which does not have the abovementioned disadvantages. Surprisingly it has now been found that a polyether ester based on terephthalic acid, isophthalic acid, 1,4-butanediol and a polyalkylene ether diol, characterized in that the molar ratio of terephthalic acid to isophthalic acid is from 35 to 50:from 65 to 50, in particular from 42 to 47:from 58 to 53, and polyethylene glycol is employed in a proportion of from 10.5 to 25% by weight and with a molecular mass of from 0.4 to 6 kg/mol, based on the sum of all of the radicals present in the polyether ester, meets these requirements. The molar ratio of terephthalic acid to isophthalic acid is preferably 42:58 and 45:55.
Up to 20 mol % of the isophthalic acid or terephthalic acid employed can be replaced by adipic acid and/or another saturated dicarboxylic acid of 6 to 12 carbon atoms.
Highly surprisingly it has now been found that products with such high proportions of isophthalic acid in conjunction with polyethylene glycol can be processed and milled without problems, which appeared impossible on the basis of knowledge gained to date. Furthermore, melting points lower by almost 20.degree. C. were found (DSC; from 103.degree. to 108.degree. C.), which comes closer to the recent trend in bonding. Combined with this is a substantially higher degree of adhesion to critical outer materials. In spite of this it has been possible to achieve a large reduction in back-sticking.
Up to 20 mol % of the 1,4-butanediol, preferably from 5 to 10 mol %, can be replaced by hexanediol.
Up to 10% by weight of the polyethylene glycol used can be replaced by di- or triethylene glycol or by low molecular weight alkylene ether diols.
As is known, polyethylene glycol imparts to polyether esters prepared therefrom a particularly high level of susceptibility to thermal oxidation, which is why stabilizers should expediently be used in the preparation of the polyether ester (H. Zimmermann, K. Dietrich, Acta Polym. 1979, 30(4) 199-203).
In practice, further additives such as nucleating agents, for example micronized talc, antistatics, lubricants or waxes as milling assistants, are added either directly to the polyether ester melts, or during or after the milling of the polyether esters.
The polyether esters are prepared in principle by the customary melt condensation processes, as are described, for example, in DE-C 31 32 059.